This four-year study will evaluate treatment outcomes of an innovative drug treatment and HIV/AIDS prevention program begin implemented in the Massachusetts state prisons by a contractor, Spectrum Addiction Services, Inc. The state's Department of Correction (DOC) and Spectrum have developed an innovative six-month residential program, being implemented in the fall of 1993, that will be delivered in a uniform manner in six different facilities. Priority for treatment will be given to those diagnosed as being a high-risk of relapse and/or recidivism. The study will take advantage of the shortfall of available treatment slots relative to expected demand to conduct a controlled experiment. An estimated 7,000 prisoners currently in custody, and at least two-thirds of the 2,400-plus incoming prisoners each year, have histories of drug- involvement and abuse. The capacity of the program will be limited to treating approximately 1,100 per year. To allocate these scarce treatment slots, prisoners will be screened for admission to treatment and the pool of offenders identified as suitable will then be selected for treatment by random assignment. This will yield two populations, having 700 subjects each: "experimentals" assigned to the drug treatment program, and "controls" not so assigned. Subjects will be given baseline interviews shortly after release from prison, and reinterviewed at four months and twelve months following release. Treatment outcome measures will include time to relapse to sustained drug abuse and, separately, time to commission of a crime and time to resumption of HIV risk behavior. Indicators of these outcomes events will include self-reported relapse, criminality, and HIV-risk behaviors, urine tests, and official criminal justice records.